The increased use of photonic devices in many applications is driving the need for reduced cost and improved assembly methods. One of the major difficulties in using photonic devices is the coupling to optical fibres required for transmission from one photonic device to another. Efficient, simple methods of coupling the photonic devices at both ends of the optical link are highly desirable.
Existing photonic devices include lasers, detectors, modulators, switches, attenuators, optical multiplexers and de-multiplexers, gratings, couplers and other devices where a function is achieved in a photonic device. Photonic devices are manufactured from a variety of materials including silica, silicon, silicon-Germanium, Indium Phosphide, Gallium Arsenide, Lithium Niobate and other materials that exhibit optical emitting, detection, or guiding properties.
Existing methods for coupling photonic devices to optical fibres efficiently include some form of mode matching because the optical waveguides have a different size than the core of an optical fibre. One method of mode matching involves using lenses. The use of lenses for mode matching adds cost and manufacturing complexity to the photonic device. An alternative method of mode matching involves manufacturing a V groove adjacent to the waveguide such that the optical fibre can locate in the V groove and be correctly positioned with respect to the waveguide. The V groove method requires larger photonic devices to provide space for the V groove which increases the cost of the photonic device. Additionally, manufacturing the V grooves requires additional processing steps compared to manufacturing integrated photonic devices without V grooves, which also increases the cost of the photonic device.
Another method of mode matching involves producing a tapered region in a waveguide during the manufacturing of the photonic device. Creating a tapered region in the waveguide addresses the issues created because the optical waveguides have a different size than the core of the optical fibre. By using a tapered region in the waveguide for mode matching, it is possible to butt couple the optical fibre to the waveguide and obtain efficient transfer of light between the waveguide and the optical fibre. Butt coupling removes the need for lensing and complicated alignment procedures and is the preferred option for integrated photonic assemblies. Accordingly, a method is required to efficiently and easily butt couple optical fibre to a photonic device using the edge of the waveguide.